Filming apparatus

ABSTRACT

System for the vacuum deposition of thin films on sheet material including a plurality of vacuum chambers arranged in end-to-end relation to one another, one of the chambers constituting a filming chamber, valve compartments disposed between adjacent chambers for placing them in communication when open and separating them when closed together with similar compartments located at the respective entry and exit ends of the plurality of chambers, conveying means for moving sheet material through successive chambers and including carriers for clamping individual sheets along their upper edges and maintaining same in a substantially vertical position, means responsive to the positioning of the material in the chambers to permit opening and closing of the valve compartments in predetermined sequence, and means outwardly of the entry and exit valve compartments for aligning and positioning the sheet material for travel through the chambers and subsequent unloading thereof.

I United States Patent [I51 3,673,981 Beckham et al. July 4, 1972 [s41 FILMING APPARATUS 3,262,420 7/1966 Bossi et al .1 l8/S7 [72] Inventors: Robert R. Bcckham; Emmett L. Walters; 349l'720 1/1970 Hams 118/495 izg f g'm i g t y g FOREIGN PATENTS OR APPLICATIONS o e l 9,024 1912 Great Britain ,266/4 B [731 Asi'gmZ gg zf m! 56l,408 5/1944 Great Britain ..266/4 8 22 l d; May 13 1969 Primary Examiner-Morris Kaplan [211 A l N 862 998 Attorney-Collins & Oberlin Related [1.8. Application Data [57] ABSTRACT [60] Division of Ser No 664 440 Au 1967 Pat No System for the vacuum deposition of thin films on sheet 3 495 724 whi'ch a fi an material including a plurality of vacuum chambers arranged in 2 1 29 I966 abandoned p end-to-end relation to one another, one of the chambers cony stituting a filming chamber, valve compartments disposed between adjacent chambers for placing them in communica- C l lllllllllllllllllllllllllllllll "us/6 I 36 tion when open and separating them when closed together [58] Field 8 4849 5 with similar compartments located at the respective entry and b h exit ends of the plurality of chambers, conveying means for moving sheet material through successive chambers and including carriers for clamping individual sheets along their [56] References Cited upper edges and maintaining same in a substantially vertical UNITED STATES PATENTS position, means responsive to the positioning of the material in the chambers to pennit opening and closing of the valve com- 1,876,960 9/1932 Kenworthy ..266/4 B UX panmems in predetermined Sequence. and means outwardly is 5/1934 Owen B UX of the entry and exit valve compartments for aligning and posi gran: tioning the sheet material for travel through the chambers and i y bs u ntu lo d'n the eof, 3,l97,328 7/1965 Jung etal ..m/107.2 eq c n a g r 3,206,322 9/1965 Morgan ..l l8/49 X 68 Claims, 16] Drawing Figures p a-io sen u kit PATENTEBJUL 4:972 3.673.981

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1. Apparatus for treating sheets of material, comprising a. a plurality of chambers in end to end relation to one another, one of said chambers constituting a coating chamber; b. means for conveying sheets of material successively through each of said chambers; c. carrier means supporting said sheets in a vertical position for movement along said conveying means; d. means for creating a vacuum in each of said chambers; e. means in said coating chamber for coating the sheets as they move therethrough; f. valve compartments disposed between adjacent chambers for placing them in communication when open and separating them when closed; g. valve compartments located at the respective entry and exit ends of said plurality of chambers, and h. means responsive to positioning of the carrier means in said chambers to permit opening and closing said valve compartments in predetermined sequence from the entry end to the exit end of said plurality of chambers.
 2. Apparatus for treating sheets of material as defined in claim 1, in which the means in the coating chamber for coating the sheets comprises thermal evaporation means.
 3. Apparatus for treating sheets of material as defined in claim 2, in which said thermal evaporation means comprises a plurality of electron beam evaporation sources arranged in vertical and horizontal rows positioned in at least one side wall of said coating chamber.
 4. Apparatus for treating sheets of material as defined in claim 1, in which said conveying means includes drive means in each chamber moving in a fixed horizontal path and said carrier means includes means engageable with said drive means to move said carrier means through successive chambers.
 5. Apparatus for treating sheets of material as defined in claim 4, in which the means on said carrier means engageable with said drive means comprise magnetic means.
 6. Apparatus for treating sheets of material as defined in claim 4, in which said drive means comprises an endless chain belt in each of said chambers traveling in a horizontal path, and in which said carrier means comprises a plurality of individual carriers, and means on each carrier for magnetically connecting the carrier to the endless chain belt in each succeeding chamber to move the carriers therethRough.
 7. Apparatus for treating sheets of material as defined in claim 6, in which said last named means comprises spaced permanently magnetized members carried by each carrier and magnetically attracted to and moved along by each succeeding chain belt, the distance between adjacent chain belts being less than the distance between the magnetized members on each carrier.
 8. Apparatus for treating sheets of material as defined in claim 1, in which said coating chamber comprises an entry area, a coating area and an exit area, and including: a. individual conveyors in said entry area, coating area, and exit area for successively receiving the carrier means supporting said sheets; b. means for driving the conveyor in the entry area at a predetermined constant speed; c. means for driving the conveyor in the coating area at a predetermined constant speed substantially less than the speed of the conveyor in the entry area; d. means for driving the conveyor in the exit area at a predetermined constant speed substantially greater than the speed of the conveyor in the coating area, and e. means for reducing the speed of the conveyor in the entry area to that of the conveyor in the coating area when the carrier means is received in said entry area.
 9. Apparatus for treating sheets of material as defined in claim 8, in which each of said conveyors comprises an endless chain belt traveling in a horizontal path and said carrier means includes a plurality of individual carriers, and including means for successively magnetically connecting each carrier to the chain belt in the entry coating, and exit areas to advance said carrier through the coating chamber.
 10. Apparatus for treating sheets of material as defined in claim 9, in which said last named means comprises spaced permanently magnetized members carried by each carrier and magnetically attracted to and moved along by each succeeding chain belt, the distance between adjacent chain belts being less than the distance between the magnetized members on each carrier.
 11. Apparatus for treating sheets of material, comprising: a. a plurality of chambers including an entry chamber, an exit chamber and a plurality of intermediate chambers in end to end relation to one another, one of said intermediate chambers constituting a coating chamber; b. conveyor means in each of said chambers; c. a plurality of carriers mounted for movement along said conveying means; d. means carried by said carriers for supporting the sheets in a vertical position; e. means for creating a vacuum in each of said intermediate chambers; f. thermal evaporation means in said coating chamber; g. a first valve compartment at the entry end of the entry chamber, a second valve compartment at the exit end of the exit chamber and valve compartments between each intermediate chamber and the adjacent chambers for placing them in communication with one another when open and separating them when closed; h. means for individually raising and lowering the pressure in the entry chamber and exit chamber; i. conveyor means positioned outwardly of said entry chamber; j. means responsive to a predetermined relatively high pressure in said entry chamber to open the valve compartment at the entry end thereof to permit passage of a carrier from said last-named conveyor means into said entry chamber, and k. means automatically operable when said carrier reaches a predetermined position in said entry chamber to close the valve compartment at the entry end thereof.
 12. Apparatus for treating sheets of material as defined in claim 11, including: a. means operable by said responsive means for initiating operation of the conveyor means outwardly of the entry chamber and also within said entry chamber to move a carrier into the said entry chamber, and b. means engageable by said carrier when it is received in said entry chamber to bring both of said conveyor means to a stop.
 13. ApparaTus for treating sheets of material as defined in claim 11, including: a. means in said entry chamber responsive to a predetermined relatively low pressure therein to open the valve compartment between the entry chamber and adjacent intermediate chamber to permit passage of a carrier from said entry chamber into said intermediate chamber, and b. means automatically operable to close said last-named valve compartment when said carrier reaches a predetermined position in said intermediate chamber.
 14. Apparatus for treating sheets of material as defined in claim 13, including: a. means operable by said low pressure responsive means for initiating operation of the conveyor means in said entry chamber and adjacent intermediate chamber, and b. means engageable by said carrier when it is received in said intermediate chamber to bring both of said conveyor means to a stop.
 15. Apparatus for treating sheets of material as defined in claim 13, including: a. means responsive to a predetermined relatively low pressure in the exit chamber to open the valve compartment between said exit chamber and the adjacent intermediate chamber to permit the passage of a carrier from said intermediate chamber into said exit chamber, and b. means automatically operable to close said last-named valve compartment when said carrier reaches a predetermined position in said exit chamber.
 16. Apparatus for treating sheets of material as defined in claim 15, including: a. means operable by said last-named responsive means for initiating operation of the conveyor means in said intermediate chamber and in said exit chamber, and b. means engageable by said carrier when it is received in said exit chamber to bring both of said conveyor means to a stop.
 17. Apparatus for treating sheets of material as defined in claim 15, including: a. conveyor means positioned outwardly of said exit chamber; b. means responsive to a predetermined relatively high pressure in said exit chamber to open the valve compartment at the exit end thereof to permit passage of a carrier from said exit chamber to the conveyor means outwardly thereof, and c. means automatically operable to close said last-named valve compartment when said carrier reaches a predetermined position on said conveyor means positioned outwardly of said exit chamber.
 18. Apparatus for treating sheets of material as defined in claim 17, including: a. means operable by said second low pressure responsive means in said exit chamber for initiating operation of the conveyor means in said exit chamber and the conveyor means outwardly thereof, and b. means engageable by said carrier when it is received on said conveyor means located outwardly of said exit chamber to bring both of said conveyor means to a stop.
 19. Apparatus for treating sheets of material, comprising: a. a plurality of chambers arranged in end to end relation and including in succession: I. an entry chamber, II. a cleaning chamber, III. a heating chamber, IV. a coating chamber, V. a cooling chamber, and VI. an exit chamber; b. conveyor means in each of said chambers; c. a plurality of carriers for suspending sheets in vertical position mounted on said conveying means and movable through each of the chambers at a substantially constant rate of speed; d. a first valve compartment at the entry end of the entry chamber, a second valve compartment at the exit end of the exit chamber, and valve compartments between each two adjacent intermediate chambers for placing said chambers in communication with one another when open and separating them when closed; e. means for independently regulating the pressure in each of said chambers, and f. means controlled by the pressure in said chambers for opening and closing said valve compartments in predetermined sequence.
 20. Apparatus for treating sheets of material as defined in claim 19, in which each valve compaRtment includes a panel and individual means for opening and closing said panels.
 21. Apparatus for treating sheets of material as defined in claim 19, including: a. means in the cleaning chamber for cleaning the sheets; b. means in the heating chamber for heating the sheets, and c. means in the coating chamber for coating the sheets.
 22. Apparatus for treating sheets of material as defined in claim 21, in which the means in the coating chamber for coating the sheets comprises thermal evaporation means.
 23. Apparatus for treating sheets of material as defined in claim 22, in which said thermal evaporation means comprises a plurality of electron beam evaporation sources arranged in vertical and horizontal rows positioned in at least one side wall of said coating chamber.
 24. Apparatus for treating sheets of material as defined in claim 21, in which the means in the cleaning chamber for cleaning the sheets comprises glow discharge means.
 25. Apparatus for treating sheets of material as defined in claim 19, in which a. the cleaning chamber includes glow discharge cleaning means, and b. the coating chamber includes thermal evaporation coating means.
 26. Apparatus for treating sheets of material as defined in claim 19, including: a. conveyor means positioned outwardly of said entry chamber; b. said means for opening and closing including means responsive to a predetermined relatively high pressure in said entry chamber to open the valve compartment at the entry end thereof to permit passage of carriers into said entry chamber, and c. means automatically operable to close said last-named valve compartment when said carriers reach a predetermined position in said entry chamber.
 27. Apparatus for treating sheets of material as defined in claim 26, including: a. means operable by said responsive means for initiating operation of the conveyor means outwardly of the entry chamber and within the entry chamber to move carriers from the former conveyor means onto the latter conveyor means, and b. means engageable by said carriers in said entry chamber to bring both of said conveyor means to a stop.
 28. Apparatus for treating sheets of material as defined in claim 19, including: a. said means for opening and closing including means in said entry chamber responsive to a predetermined relatively low pressure therein to open the valve compartment between the entry chamber and the cleaning chamber to permit passage of carriers from said entry chamber into said cleaning chamber, and b. means automatically operable to close said last-named valve compartment when said carriers reach a predetermined position in said cleaning chamber.
 29. Apparatus for treating sheets of material as defined in claim 28, including: a. means operable by said low pressure responsive means for initiating operation of the conveyor means in said entry and in said cleaning chambers, b. means engageable by said carriers when received in said cleaning chamber to bring both of said conveyor means to a stop.
 30. Apparatus for treating sheets of material as defined in claim 19, including: a. said means for opening and closing including means in said cleaning chamber responsive to a predetermined relatively low pressure therein to open the valve compartment between the cleaning chamber and the heating chamber to permit passage of carriers from said cleaning chamber into said heating chamber, and b. means automatically operable to close said last-named valve compartment when said carriers reach a predetermined position in said heating chamber.
 31. Apparatus for treating sheets of material as defined in claim 30, including: a. means operable by said low pressure responsive means in said cleaning chamber for initiating operation of the conveyor means in said cleaning chamber and in said heating chamber, and b. means engageable by said carriers when received in said heating chamber to bring both of said convEyor means to a stop.
 32. Apparatus for treating sheets of material as defined in claim 19, in which said coating chamber comprises an entry area, a coating area and an exit area, and including: a. conveyor means in each of said areas; b. means for driving the conveyor means in the entry area at a predetermined relatively constant high speed; c. means for driving the conveyor means in the coating area at a predetermined constant speed substantially less than the speed of the conveyor means in the entry area; d. means for synchronizing the speed of the conveyor means in the entry area with the speed of the conveyor means in the coating area preparatory to movement of the carriers into said coating area; e. means for driving the conveyor means in the exit area at a predetermined constant speed substantially greater than the speed of the conveyor means in the coating area, and f. means for synchronizing the speed of the conveyor means in the exit area with the speed of the conveyor means in the coating area preparatory to movement of the carriers into the exit area to maintain a continuous movement of said carriers through said coating area.
 33. Apparatus for treating sheets of material as defined in claim 32, in which said synchronizing means includes: a. speed changing means interposed in the driving means for the conveyor means in the entry area to cause said entry area conveyor means to be driven by and at the reduced speed of the conveyor means in the coating area when the driving means for the entry area conveyor means is disconnected to effect passage of the carriers from the entry area into the coating area at the reduced speed of the coating area conveyor means, and b. speed changing means interposed in the driving means for the conveyor means in the exit area to cause said exit area conveyor means to be driven by and at the speed of the conveyor means in the coating area when the driving means for the exit area conveyor means is disconnected to effect passage of the carriers from the coating area into the exit area at the reduced speed of the coating area conveyor means.
 34. Apparatus for treating sheets of material as defined in claim 19, in which the coating chamber comprises an entry area, a coating area and an exit area, and including: a. said means for opening and closing including means in said heating chamber responsive to a predetermined pressure therein to open the valve compartment between the heating chamber and the coating chamber to permit passage of carriers from said heating chamber into said coating chamber, and b. means automatically operable to close said last-named valve compartment when said carriers reach a predetermined position in the entry area of the coating chamber.
 35. Apparatus for treating sheets of material as defined in claim 34, in which the conveying means in the coating chamber comprises individual conveyor means in the entry area, the coating area and the exit area, and including: a. means operable by said responsive means in said heating chamber for initiating operation of the conveyor means in the entry area of said coating chamber and in the said heating chamber, and b. means engageable by said carriers when received in said entry area of the coating chamber to bring the conveyor means in said heating chamber to a stop while the conveyor means in the coating chamber continue to operate to move the carriers therethrough.
 36. Apparatus for treating sheets of material as defined in claim 35, in which the conveyor means in the entry area, in the coating area and in the exit area of the coating chamber comprise stationary support means and endless chain belts associated therewith and mounted for movement in a horizontal path, and including: a. individual motors for driving said chain belts at predetermined constant speed; b. sprockets about which each chain belt is trained; c. a shaft connected to one of the sprockets for each chain belt and drIven by the respective motor for driving said chain belt; d. drive connections between the shaft for the chain belt in the entry area and the shaft for the chain belt in the coating area; e. means engageable by said carriers when received on the stationary support means in said entry area to disconnect the shaft from the respective motor and to simultaneously bring said motor to a stop, and f. means interposed in said drive connections for causing the chain belt in the entry area to be driven at a speed less than said predetermined constant speed by the motor for the chain belt in the coating area when the motor for the chain belt in said entry area has been stopped.
 37. Apparatus for treating sheets of material as defined in claim 36, including: a. drive connections between the shaft for the chain belt in the coating area and the drive shaft for the chain belt in the exit area, and b. means interposed in said drive connections for causing the chain belt in the exit area to be driven at a speed less than said predetermined constant speed by the motor for the chain belt in the coating area when the motor for driving the chain belt in said exit area is stopped.
 38. Apparatus for treating sheets of material as defined in claim 37, including: a. electrical pulsing means driven by the shaft for the chain belt in the coating area to produce a series of regularly spaced pulsations according to the predetermined relatively slow constant speed of said shaft; b. counting means for recording the series of pulsations; c. switch means engageable by said carrier in the coating area to initiate operation of the counting means with said electrical pulsing means; d. second electrical pulsing means driven by the shaft for the chain belt in the entry area to produce a series of regularly spaced pulsations according to the predetermined relatively high constant speed of said motor; e. second counting means for recording the second series of pulsations; f. switch means engageable by a succeeding carrier when received in said entry area to initiate operation of said second counting means with the second pulsing means in said entry area; g. pulsation totalizing means operable to receive the relatively slow pulsations of the first counting means in said coating area and the pulsations at the predetermined relatively high constant speed of the second counting means in the entry area to establish a balanced condition therebetween, and h. means operable when the balanced condition of pulsations has been established by said totalizing means to bring the motor for the chain belt in the entry area to a stop with the said succeeding carrier spaced a predetermined distance from the preceding carrier.
 39. Apparatus for treating sheets of material as defined in claim 36, including means engageable by said carrier in the exit area to initiate operation of the motor for the chain belt in said exit area to drive the chain belt in said exit area at a predetermined relatively high constant speed.
 40. Apparatus for treating sheets of material as defined in claim 39, in which the conveyor means in the cooling chamber, comprises: a. an endless chain belt mounted for movement in a horizontal path; b. sprockets about which said chain belt is trained; c. a motor for driving said chain belt; d. means engageable by a carrier in the exit area of the coating chamber to initiate operation of the motor for the chain belt in the cooling chamber; e. means in said cooling chamber responsive to a predetermined low pressure therein to open the valve compartment between the coating chamber and cooling chamber to permit passage of the carrier from the coating chamber into said cooling chamber, and f. means automatically operable to close said valve compartment when said carrier reaches a predetermined position in said cooling chamber.
 41. Apparatus for handling sheets of material as claimed in claim 40, including; a. means engageable by said carrier when said carrier reaches a predetermined position in the cooling chamber to bring the motor for the chain belt in said cooling chamber to a stop, and b. means simultaneously responsive to stopping of the last-named chain belt to bring the motor for the chain belt in the exit area of the coating chamber to a stop whereby the motor for the chain belt in the coating area of said coating chamber will drive the chain belt in said exit area at the said predetermined relatively slow speed.
 42. Apparatus for handling sheets of material as defined in claim 19, including: a. said means for opening and closing including means responsive to a predetermined relatively low pressure in the exit chamber and said cooling chamber to open the valve compartment therebetween to permit passage of carriers from said cooling chamber into said exit chamber; b. means automatically operable to close said last-named valve compartment when said carriers reach a predetermined position in said exit chamber; c. means operable by said last-named responsive means for initiating operation of the conveyor means in said cooling chamber and exit chamber, and d. means engageable by said carriers in said exit chamber to bring both of said conveyor means to a stop.
 43. Apparatus for treating sheets of material as defined in claim 19, including: a. conveyor means positioned outwardly of said exit chamber; b. said means for opening and closing including means responsive to a predetermined relatively high pressure in said exit chamber to open the valve compartment at the exit end thereof to permit passage of carriers from said exit chamber to the conveyor means outwardly thereof; c. means automatically operable to close said last-named valve compartment when said carriers reach a predetermined position on said outwardly positioned conveyor means; d. means operable by said responsive means in said exit chamber for initiating operation of the conveyor means in said exit chamber and said conveyor means outwardly thereof, and e. means engageable by said carriers on said outwardly disposed conveyor means to bring both of said conveyor means to a stop.
 44. Apparatus for treating sheets of material as defined in claim 19, in which the pressures in the entry chamber, cleaning chamber, cooling chamber, and exit chamber are variable and the pressures in the heating chamber and coating chamber are maintained substantially equal and constant.
 45. Apparatus for treating sheets of material as defined in claim 19, including: a. conveyor means positioned outwardly of the entry chamber; b. conveyor means positioned outwardly of the exit chamber, and c. said means for opening and closing including means responsive to predetermined pressures in said entry and exit chambers to actuate said means for opening and closing said valve compartments at the respective entry end and exit end of said chambers; d. means responsive to the position of the carriers in said plurality of chambers between said entry and exit chambers for opening and closing the valve compartments between two adjacent chambers; e. means responsive to the position of carriers in said entry chamber to close the valve compartment at the entry end thereof, and f. means responsive to the position of carriers on the outwardly disposed conveyor means to close the valve compartment at the exit end of said exit chamber.
 46. Apparatus for treating sheets of material as defined in claim 1, in which a. said conveying means includes drive means comprising an endless chain belt arranged in each chamber for movement in a fixed horizontal path; b. sprockets about which the chain belt is trained; c. individual motors for driving each chain belt, and d. a permanently magnetized member mounted on said carrier means and being magnetically attracted to the chain belts to move said carrier means along said path.
 47. Apparatus for treating Sheets of material as defined in claim 46, in which a plurality of permanently magnetized members are mounted on each carrier means and spaced from one another a distance greater than the distance between adjacent chain belts so that one magnetic member will be magnetically attracted to the chain belt in one chamber before the following magnetic member becomes disengaged from the chain belt in the preceding chamber, whereby continuous movement of the carrier means through the chambers can be maintained.
 48. Apparatus for treating sheets of material as defined in claim 1, in which said carrier means includes a. means for clamping the sheets along their upper edges to support the same in a vertical position prior to movement thereof into said chambers; b. means for automatically actuating the clamping means to clamp the sheets after said sheets have been moved into position relative thereto, and c. means for automatically actuating the clamping means to disengage the sheets after they have been removed from said chambers.
 49. Apparatus for treating sheets of material as defined in claim 48, in which said clamping means includes: a. fixed clamping members and movable clamping members mounted for pivotal and sliding movement; b. means for moving said movable clamping members downwardly and inwardly to clamp the upper edge of a sheet against said fixed clamping members, and c. means for securing said movable clamping members in clamping position.
 50. Apparatus for treating sheets of material as defined in claim 48, in which: a. said conveying means includes drive means comprising an endless chain belt arranged in each chamber for movement in a fixed horizontal path; b. sprockets about which the chain belt is trained; c. individual means for driving each chain belt, and d. a permanently magnetized member mounted on said carrier means and being magnetically attracted to said chain belts to move said carrier means through said chambers.
 51. Apparatus for treating sheets of material as defined in claim 49, in which a plurality of permanently magnetized members are mounted on each carrier means and spaced from one another a distance greater than the distance between adjacent chain belts so that one magnetic member will be magnetically attracted to the chain belt in one chamber before the following magnetic member becomes disengaged from the chain belt in the preceding chamber, whereby continuous movement of the carrier means through the chambers can be maintained.
 52. Apparatus for treating sheets of material as defined in claim 19, including: a. conveyor means spaced in parallel side-by-side relation in each chamber; b. carriers movable along each conveyor means for supporting sheets in a vertical position, and c. a single source of power for driving both of said carriers to move said sheets in unison.
 53. Apparatus for treating sheets of material as defined in claim 19, in which said conveyor means comprises a pair of spaced parallel monorails mounted in each chamber and including a. an endless chain belt disposed opposite each monorail; b. carriers supported by and movable along said monorails; c. permanently magnetized members mounted on each carrier and magnetically attracted to the respective chain belt, and d. means for simultaneously driving said chain belts to move the carriers in unison.
 54. Apparatus for treating sheet materials as defined in claim 19, in which said conveyor means comprises: a. drive means including an endless chain belt arranged in each chamber for movement in a horizontal path; b. sprockets about which each chain belt is trained; c. individual means for driving each chain belt, and d. a permanently magnetized member mounted on each carrier and being magnetically attracted to said chain belts to move said carrier along said path.
 55. Apparatus for treating sheets of material as claimed in claim 54, in which a plurality of permAnently magnetized members are mounted on each carrier and spaced from one another a distance greater than the distance between adjacent chain belts so that one magnetic member will be attracted to the chain belt in one chamber before the following magnetic member becomes disengaged from the chain belt in the preceding chamber whereby continuous movement of the carriers through the chambers can be maintained.
 56. Apparatus for treating sheets of material as defined in claim 19, in which the carriers include: a. means for clamping the sheets along their upper edges to support the same in a vertical position prior to movement of the carriers into said entry chamber; b. means for automatically actuating the clamping means to clamp the sheets after said sheets have been moved into position relative thereto, and c. means for automatically actuating the clamping means to disengage the sheets after said carriers have been removed from said chambers.
 57. Apparatus for treating sheets of material as claimed in claim 56, in which said clamping means includes: a. fixed clamping members and movable clamping members mounted for pivotal and sliding movement; b. means for moving the movable clamping members downwardly and inwardly to clamp the upper edge of a sheet against said fixed clamping members, and c. means for securing the movable clamping members in clamping position.
 58. Apparatus for treating sheets of material as defined in claim 56, in which said conveyor means comprises: a. drive means including an endless chain belt arranged in each chamber for movement in a horizontal path; b. sprockets about which each chain belt is trained; c. individual means for driving each chain belt, and d. a permanently magnetized member mounted on each carrier and being magnetically attracted to the chain belts to move the said carrier along said path.
 59. Apparatus for treating sheets of material as defined in claim 58, in which a plurality of permanently magnetized members are mounted on each carrier and spaced from one another a distance greater than the distance between adjacent chain belts so that one magnetic member will be attracted to the chain belt in one chamber before the following magnetic member becomes disengaged from the chain belt in the preceding chamber whereby continuous movement of the carrier through the chambers can be maintained.
 60. Apparatus for handling sheets of material as claimed in claim 1, including: a. a return conveyor located in spaced parallel relation to the plurality of chambers and having an entry end and an exit end transversely aligned with exit end and entry and respectively of the plurality of chambers; b. a transfer carriage; c. means for supporting the transfer carriage for transverse movement from a position in alignment with the exit end of the chambers to a position in alignment with the entry end of the return conveyor; d. drive means on the transfer carriage for moving a carrier means from the exit end of said chambers onto the transfer carriage; e. means engageable by the carrier means when received on the transfer carriage to bring said drive means to a stop; f. means operable automatically when the first drive means is stopped to reverse the operation thereof for subsequent movement of said carrier means from said transfer carriage; g. second drive means on said transfer carriage; h. means responsive to stopping of the first drive means to initiate operation of the second drive means for moving the transfer carriage along the supporting means to a position in alignment with the entry end of the return conveyor, i. means engageable by said transfer carriage when the same reaches a position in alignment with the entry end of the return conveyor to bring said second drive means to a stop, j. means operable automatically when said second drive means is stopped to reverse operation thereof for subsequent movement of the transfer carriage from the position in alignment with the entry end of said return conveyor, and k. means responsive to stopping of said second drive means to initiate operation of the first drive means to remove the carrier means from the transfer carriage onto the entry end of the return conveyor.
 61. Apparatus for handling sheets of material as defined in claim 60, including: a. drive means on the return conveyor, and b. means associated with said last-named responsive means for simultaneously initiating operation of said drive means on the return conveyor to move the carrier means along said return conveyor when said carrier means is removed from said transfer carriage by said first drive means.
 62. Apparatus for handling sheets of material as defined in claim 60, including: a. means engageable by the carrier means when received on the return conveyor to bring the said first drive means to a stop; b. means responsive to stopping of the first drive means to initiate operation of the second drive to return the transfer carriage to a position in alignment with the exit end of the chambers, and c. means engageable by said transfer carriage at said position of alignment to bring the second drive means to a stop.
 63. Apparatus for handling sheets of material as defined in claim 60, including: a. drive means adjacent the exit end of the return conveyor; b. a sheet unloading unit adjacent to and aligned with the exit end of the return conveyor; c. a stationary conveyor mounted above the sheet unloading unit; d. drive means on the stationary conveyor; e. a bridging conveyor interposed between the exit end of the return conveyor and the stationary conveyor and in alignment therewith; f. drive means on the bridging conveyor; g. means engageable by the carrier means adjacent the exit end of the return conveyor to initiate operation of the drive means on the stationary conveyor and the drive means on the bridging conveyor to move the carrier means from said return conveyor, across said bridging conveyor and onto said stationary conveyor, h. means engageable by the carrier means when it reaches a predetermined position on the said stationary conveyor to bring the said carrier means to a stop above said unloading unit, and i. means for releasing the sheet from said carrier means onto said unloading unit.
 64. Apparatus for handling sheets of material as defined in claim 63, including means responsive to stopping of the carrier means on said stationary conveyor to initiate operation of the sheet unloading unit to receive the sheet from said carrier means.
 65. Apparatus for handling sheets of material as defined in claim 63, including: a. an entry conveyor adjacent to and aligned with the entry end of the plurality of chambers; b. drive means on the entry conveyor; c. a shuttle carriage for receiving said carrier means from the stationary conveyor after the sheet has been released therefrom; d. means supporting the shuttle carriage for transverse movement between a position in alignment with the exit end of the return conveyor and a position in alignment with the entry conveyor; e. first drive means on the shuttle carriage to move the same transversely into engagement with said bridging conveyor to displace the bridging conveyor and assume its position in alignment with the exit end of the return conveyor; f. means engageable by said shuttle carriage when it reaches the position in alignment with the exit end of the return conveyor to bring said first drive means to a stop; g. a second drive means on the shuttle carriage; h. means responsive to stopping of said first drive means to initiate operation of the second drive means and the drive means on the stationary conveyor to move the carrier means from the stationary conveyor onto said shuttle carriage; i. means engageable by the carrier means when it reaches a predetermined position on the shuttle carriage to Bring the second drive means on said shuttle carriage and the drive means on the stationary conveyor to a stop; j. means also responsive to stopping of the second drive means to initiate operation of said first drive means on the shuttle carriage to move said shuttle carriage toward a position in alignment with said entry conveyor; k. a sheet loading unit, and l. means for moving said carrier means from said shuttle carriage into position to receive a sheet from said loading unit.
 66. Apparatus for handling sheets of material as defined in claim 65, in which the sheet loading unit is located adjacent to and in alignment with the entry conveyor; and including: a. a second stationary conveyor mounted above the sheet loading unit; b. drive means on the second stationary conveyor; c. a second bridging conveyor interposed between the entry conveyor and the stationary conveyor and in alignment therewith; d. drive means on the second bridging conveyor; e. means engageable by the shuttle carriage when it reaches the position in alignment with the second stationary conveyor to bring said first drive means to a stop, and f. means responsive to stopping of said first drive means on the shuttle carriage to initiate operation of the second drive means on said shuttle carriage and the drive means on the second stationary conveyor to move the carrier means from the shuttle carriage onto said second stationary conveyor above said sheet loading unit to receive a sheet therefrom.
 67. Apparatus for handling sheets of material as defined in claim 66, including means responsive to stopping of the carrier means on the second stationary conveyor to initiate operation of the sheet loading unit to secure a sheet in vertical position on the carrier means.
 68. Apparatus for handling sheets of material as defined in claim 67, including a. means responsive to securing of the sheet on the carrier means to initiate operation of the drive means on the entry conveyor, the drive means on the second bridging conveyor and the drive means on the second stationary conveyor for moving the carrier means from the second stationary conveyor across the second bridging conveyor and onto the entry conveyor, and b. means engageable by the carrier means when it reaches a predetermined position on said entry conveyor to bring said carrier means to a stop. 